Biology subjects

Bok, J. W.

Publications and source records attributed to Bok, J. W..

5 recordsLinked to original sources

bioRxiv2026

The Aspergillus fumigatus C2-Domain Protein SppA is required for septal integrity and alters susceptibility to echinocandins and neutrophil killing during infection

Aspergillus fumigatus is a major opportunistic fungal pathogen whose ability to maintain hyphal integrity and withstand host defenses is critical for virulence. Septal pores, which connect hyphal compartments, are dynamically regulated to preserve cellular integrity under stress, yet the molecular components governing this process remain incompletely defined. Here, we identify and characterize a septal pore-associated protein, SppA, and demonstrate its essential role in maintaining septal integrity in A. fumigatus. We show that expression of SppA is positively regulated by the transcription factor ZfpA and is induced in response to the cell wall-targeting antifungal caspofungin. Deletion of sppA resulted in defective septal organization and increased susceptibility to hyphal damage. The mutant exhibited heightened sensitivity to cell wall-targeting antifungal agents, indicating a role in cell wall stress tolerance. In a zebrafish model of invasive aspergillosis, loss of SppA significantly attenuated virulence which was abrogated in neutrophil-deficient zebrafish. Further, the mutant strain displayed increased susceptibility to killing by primary human neutrophils, suggesting that proper septal pore formation contributes to fungal survival during host immune attack. Together, our findings establish SppA as a critical determinant of septal integrity, antifungal tolerance, and pathogenicity in A. fumigatus, and position it as part of a ZfpA-regulated, caspofungin-responsive pathway that supports fungal survival during stress and infection. Author SummaryAspergillus fumigatus is a common environmental mold that can cause life-threatening infections in people with weakened immune systems. For successful invasion of host tissue, the fungus requires the ability to protection sections of its hyphae from cell wall targeting antifungals and host immune cell attack by closing septal (cross wall) pores distributed throughout hyphal strands. We have identified an A. fumigatus protein, SppA, required for proper septal pore closure. Loss of SppA reduces the ability of hyphae to withstand treatment with antifungals and the ability of A. fumigatus to cause disease in a zebrafish infection model. The SppA mutant was particularly susceptible to killing by neutrophils, key immune cells that help control fungal infections. Our findings reveal an important mechanism that helps A. fumigatus survive environmental and host-imposed stresses and highlight septal pore regulation as a potential target for future antifungal strategies.

microbiology↗

bioRxiv2026

An Aspergillus lncRNA atlas reveals a novel modulator of aflatoxin biosynthesis

Long non-coding RNAs (lncRNAs) represent a significant fraction of the transcriptome and are vital regulators in eukaryotes, yet their functional landscape in fungi remains largely undefined. Here we present a transcriptomic atlas of 8,553 lncRNAs across four evolutionarily and biotechnologically diverse Aspergillus species. We observed marked diversity in the long non-coding repertoire between species, with only 39% shared between at least two species. However, conserved lncRNAs are expressed at significantly higher levels and across more conditions than species-specific ones, revealing a functional hierarchy within the non-coding transcriptome. We also identify subtelomeres and transposable elements as hotspots for lncRNA innovation in Aspergillus, albeit at the cost of reduced expression. Integrating genomic and transcriptomic data, we show that lncRNAs predominantly exhibit distance-dependent cis-coexpression with neighboring genes and, through guilt-by-association, we identify their participation in global modules governing primary and secondary metabolism. This framework enabled the discovery of aflalinc, a species- and condition-specific lncRNA in A. flavus that plays a role in regulating the aflatoxin biosynthetic gene cluster. Crucially, deletion of this lncRNA severely reduced the production of aflatoxin B, a highly potent agent of acute toxicity and driver of hepatocarcinoma, without affecting growth, conidiation, or sclerotia formation. In addition, examination of an independent dataset confirms the strength of the co-expression networks and uncovers stage-specific functions for lincRNAs in the maturation of A. fumigatus biofilms. Together, these findings establish lncRNAs as integral components of fungal biology and demonstrate that they can modulate mycotoxin production and biofilm formation, with broad implications for controlling fungal threats to food safety and human health.

microbiology↗

bioRxiv2026

Endosome motility controls light-responsive reproductive development and secondary metabolite production in Aspergillus

Filamentous fungi, such as Aspergillus species, use microtubule transport to move early endosomes. Other cargos, such as peroxisomes and mRNAs, "hitchhike" on early endosomes to move throughout the long hyphae of these organisms. In Aspergillus nidulans, peroxisomes hitchhike on early endosomes using the endosomal protein PxdA and the peroxisomal protein AcbdA. The HookA adaptor protein links endosomes to microtubule motors. Here, we set out to explore the physiological functions of peroxisome hitchhiking and endosome motility. Aspergillus nidulans has a complex life cycle that includes asexual and sexual reproduction. A. nidulans and other fungi within the Pezizomycotina subphylum are also notable for the vast number of secondary metabolites they produce. Light and other environmental conditions influence developmental decisions and secondary metabolite production. Here, we found that sexual reproduction is favored in the absence of endosome motility, even in the light, which normally promotes asexual reproduction. RNA sequencing of strains lacking PxdA-marked motile early endosomes showed altered expression of genes involved in development. Unexpectedly, we also observed altered expression of genes involved in secondary metabolism in strains lacking endosome motility and peroxisome hitchhiking. Using mass spectrometry, we found that the loss of endosome motility affected the biosynthesis of secondary metabolites, including sterigmatocystin, a carcinogenic mycotoxin that is a food contaminant. Finally, in a pathogenic species, Aspergillus fumigatus, we found that deletion of its pxdA homolog also significantly altered secondary metabolite production. Our work uncovers an unexpected link between organelle motility, developmental decisions in response to light, and secondary metabolite production in filamentous fungi.

cell biology↗

bioRxiv2023

Terpenoid balance in Aspergillus nidulans unveiled by heterologous squalene synthase expression

Filamentous fungi produce numerous uncharacterized natural products (NPs) that are often challenging to characterize due to cryptic expression in laboratory conditions. Previously, we have successfully isolated novel NPs by expressing fungal artificial chromosomes (FACs) from a variety of fungal species into Aspergillus nidulans. Here, we demonstrate a new twist to FAC utility wherein heterologous expression of a Pseudogymnoascus destructans FAC in A. nidulans altered endogenous terpene biosynthetic pathways. In contrast to wildtype, the FAC transformant produced increased levels of squalene and aspernidine type compounds, including three new nidulenes (1-2, 5), and lost nearly all ability to synthesize the major A. nidulans characteristic terpene, austinol. Deletion of a squalene synthase gene in the FAC restored wildtype chemical profiles. The altered squalene to farnesyl pyrophosphate ratio leading to synthesis of nidulenes and aspernidines at the expense of farnesyl pyrophosphate derived austinols provides unexpected insight into routes of terpene synthesis in fungi. TeaserReshaping terpenes: Heterologous FAC expression reroutes terpene pathways.

microbiology↗

bioRxiv2023

Aspergillus fumigatus transcription factor ZfpA regulates hyphal development and alters susceptibility to antifungals and neutrophil killing during infection

Hyphal growth is essential for host colonization during Aspergillus infection. The transcription factor ZfpA regulates A. fumigatus hyphal development including branching, septation, and cell wall composition. However, how ZfpA affects fungal growth and susceptibility to host immunity during infection has not been investigated. Here, we use the larval zebrafish-Aspergillus infection model and primary human neutrophils to probe how ZfpA affects A. fumigatus pathogenesis and response to antifungal drugs in vivo. ZfpA deletion promotes fungal clearance and attenuates virulence in wild-type hosts and this virulence defect is abrogated in neutrophil-deficient zebrafish. ZfpA deletion also increases susceptibility to human neutrophils ex vivo while overexpression impairs fungal killing. Overexpression of ZfpA confers protection against the antifungal caspofungin by increasing chitin synthesis during hyphal development, while ZfpA deletion reduces cell wall chitin and increases caspofungin susceptibility in neutrophil-deficient zebrafish. These findings suggest a protective role for ZfpA activity in resistance to the innate immune response and antifungal treatment during A. fumigatus infection. Author SummaryAspergillus fumigatus is a common environmental fungus that can infect immunocompromised people and cause a life-threatening disease called invasive aspergillosis. An important step during infection is the development of A. fumigatus filaments known as hyphae. A. fumigatus uses hyphae to acquire nutrients and invade host tissues, leading to tissue damage and disseminated infection. In this study we report that a regulator of gene transcription in A. fumigatus called ZfpA is important for hyphal growth during infection. We find that ZfpA activity protects the fungus from being killed by innate immune cells and decreases the efficacy of antifungal drugs during infection by regulating construction of the cell wall, an important protective layer for fungal pathogens. Our study introduces ZfpA as an important genetic regulator of stress tolerance during infection that protects A. fumigatus from the host immune response and antifungal drugs.

microbiology↗